Field of the Invention
This invention relates to the classification and identification of solid propellant rockets, and more particularly to the detection and processing of the optical radiance of the rocket motor exhaust plume to classify and identify rockets.
Description of the Related Art
Rocket motors or a “rocket” is a jet engine that uses only stored propellant mass for forming its high speed propulsive jet. Since they need no external material to form their jet, rocket motors can be used for spacecraft propulsion as well as terrestrial uses such as missiles or aircraft. Rocket motors produce thrust by expulsion of a high-speed fluid exhaust. This fluid is nearly always a gas which is created by high pressure combustion of solid or liquid propellants, consisting of fuel and oxidiser components, within a combustion chamber. The fluid exhaust is then passed through a supersonic propelling nozzle which uses heat energy of the gas to accelerate the exhaust to very high speed, and the reaction to this pushes the rocket in the opposite direction.
Real-time or near real-time classification and identification of rockets via remote sensing has applications both to forensic analysis for peacekeeping operations or to live battlefield conditions to aid in the determination of a firing point to direct counter-fire or an impact point to provide advance warning to friendly troops. “Classification” generally refers to placement of the rocket within a defined class such as short, mid or long range or light, medium or heavy. For example, light rockets may range in caliber from 80 to 122 mm, medium from 122 to 200 and heavy from 200 to 240. “Identification” generally refers to the determination of a particular rocket e.g. a 107 mm rocket.
Radar installations use radio waves to determine range, altitude, direction and speed of objects. Radar can be used to detect and track the flight of a rocket based on the reflected radio frequency energy off of the rocket body. The radar unit can model the ballistic trajectory of the rocket and extrapolate forward and backward to estimate the impact point and firing point, respectively. The radar unit may attempt to classify the rocket based on its ballistic trajectory. Classification accuracy is limited and latency is dictated by having to estimate the ballistic trajectory over some portion of the flight.
Optical sensing installations use pixelated imagers to detect passive optical radiance e.g. visible or IR bands, from the rocket to form an image of the rocket. The image provides spatial information as to the size, shape and features of the rocket that can be used to classify, or possibly identify the rocket. Over useful fields of view and ranges this requires a high resolution imager. In the IR band, high resolution imagers are typically expensive. In the visible band, high resolution imagers are readily available but are limited to use in the daylight.